IT·Science Talk

How does a block of ice at the South Pole 'see' a neutrino? Nerdy question

I've read the GONOM summary: thousands of basketball-sized light sensors in a cubic kilometre of ice, catching the faint flashes when a neutrino hits an atomic nucleus.

What I don't quite get: if neutrinos barely interact with anything, how do you get enough flashes to learn anything? Is it just that a cubic kilometre is so big that rare events add up? And why ice rather than, say, a big water tank?